Process for the preparation of lithopones.



UNITED STATES PATENT OFFICE.

' Specification of Letters Patent.

Patented May 21, 1907.

Application filed November 24, Ii305. Serial No. 288.857.

To all whom it may concern:

, thus greatly limiting the use of this color.

Be it known subject oft'he King of Prussia, residing at Goslar-on-the-Harz, 4 Reussstrasse, in the Kingdom-of Prussia, Germany, have invented certain newnand useful Improvements Relating to a Process for the Preparation of Lithopones, of which the following is a full, clear, and exact description. The lithopone prepared by previous methods possesses as is well known the inconven ient has recently been endeavored to remove'this by means .of a process described in of 1903 [Great Britain] Unfortunately the ,lithopone thus producedpossessed a slightly tioned' specification to arise in the incandesaslightly yellowish color lesser degree of covering power and received from being adopted in a general manner. The combination which caused'the black nes s appears according to the above men cent process to which the lithopone is subj ected through the presence and the decomposi- 1 tion ofcorhbinationsOf chlorin (chlorid of barium, chlorid of calcium, chlorid of sodium) I chanes caused by for which reason greatv value is attached,.in the "process hitherto used, to the movalof these-combinations of chlorin. But it isjust these very combinations and the them that, asvexperience has s own, produce the favorableinflu'ence' on the covering ower and color of the product obtained. he blacknessitself' depends most probably on a reduction in the re uisite combination through the sunlight, but the'theoretical investigations on this have not yet been completed. It was-however. recognized that the transference of this combination to a higher stage eventually lead to the attainment of the de I sired result. that I, RUDoLF ALBERTI, a 1

property of turning black in sunlight obtained after which prevented it to secure by patent is:

previous resubject j of oxidation, which is no longer reduced by sunlight, must According to the present invention this has been achieved by the addition of superoxids' of alkali and alkaline earthsas well as superoxid of hydrogen to the lithopones. The best way is to add the superoxid in question to the ready lithopone that is to say after it has been submitted to the incandescent rocess and washed in suitable quantities gwhen using super-oxid of barium, experience has shown 2% to. be sufficient) While it is in the tub or tank and to stir or mix at the ordinary'or at a slightly increased temperature. The lithopone thus pressing and drying remains White in color; i

Su er-oxid of barium can also be added to the ried lithopone before reduction .in the machines used for this purpose, but in such case it is necessary to stir or mix thoroughly.

What I claim as my 1 In the preparation of lithopone, the pndcess which consists in adding a superoXid thereto. t F l 2. In the preparation of lithopone,- the process which consists in adding a superoxid of an alkaline substance thereto.

L 3. In the preparation of lithopone, the

process which consists in subjecting it to the usual incandescent treatment and subsequently adding a superoxid thereto.

,4. In the preparation of lithopone, the process which consists insubjecting it to the 'usual incandescent treatment, and washing it, and subsequently adding a" superoxid thereto.

In witness whereof, I have hereunto si ed my name in the witnesses. 4 z RUDOLF ALBERTI. Witnesses v I I JQHILDEBRANT,

I M. EIDENI'IAMMER.

invention, and desire presence of two subscri ing' 

